Building a hash in a conditional way

Question

I am using Ruby on Rails 3.0.10 and I would like to build an hash key\\value pairs in a conditional way. That is, I would like to add a key and its related value if a condition

Answer 1

Keep it simple:

hash = {
  key1: value1,
  key3: value3,
}

hash[:key2] = value2 if condition

This way you also visually separate your special case, which might get unnoticed if it is buried within hash literal assignment.